The invention relates to a charging arrangement and a charging method having a floating charging unit, the charging arrangement comprising a vehicle having a charging module in the vehicle underbody and a stationary charging station having a charging unit, in order to inductively charge a battery of the vehicle.
Within the next decade, vehicles having an electric drive, such as electric and hybrid vehicles, will increase their market shares in the automobile sector. These vehicles frequently have an external recharging possibility which is usually implemented in a wired manner. Such vehicles are therefore also called plug-in vehicles. The charging of a plug-in vehicle has to be based on a robust and lasting concept suitable for everyday driving, in order to be able to achieve a comprehensive production readiness. It is therefore a goal to facilitate an efficient comfortable charging within the scope of the public infrastructure (roads and expressways) and of the private infrastructure (parking spaces and garages). Up to now, the development has preferably been based on wired charging stations.
Increasingly, wireless charging stations with a contactless energy transmission are also being considered. This inductive charging technique is known in the state of the art. German Patent Document DE 42 36 286 A1 describes, for example, an arrangement with a vehicle-side secondary charging coil and a primary charging coil of the charging station which is guided to the vehicle on a guiding arm for charging the vehicle. Since, for establishing an optimal charging connection, the guiding arm is moved in a sensor-controlled motor-driven manner between the two coils, this is a complex and cost-intensive development. German Patent Document DE 10 2009 023 409 A1, for example, describes a vehicle docking system, where the vehicle movement is utilized for bringing a secondary charging coil at the vehicle in contact with a primary charging coil at a charging station. This makes it necessary for the driver to move the vehicle in a targeted manner, i.e. possibly with much maneuvering, into a precisely predefined target position.
It is an object of the invention to provide an improved charging arrangement and an improved charging method.
This and other objects are achieved by a charging arrangement and a charging method with a floating charging unit. The arrangement includes a vehicle having a charging module in the vehicle underbody and a stationary charging station with a charging unit, for the inductive charging of a battery of the vehicle.
According to the invention, the charging station is disposed close to the ground or in the ground. Furthermore, the charging unit is disposed in the charging station in a floating manner and has a predefined horizontal movement range. In addition, the charging module has at least one localization magnet, and the charging unit has at least one positioning magnet. The charging unit is constructed as a primary coil, and the charging module is constructed as a secondary coil.
This has the effect that, although the charging station may be disposed in a stationary manner, the charging unit carrying the primary coil is disposed to be movable in the horizontal direction, i.e. in the x-direction (longitudinal axis) and y-direction (transverse axis) of a vehicle-related coordinate system, and is not tied to any location within the horizontal movement range. The ground is particularly that plane or the area below this plane on which the wheels of the vehicles are rolling. Within the scope of this document, the terms ground and underground are synonymous.
According to a preferred embodiment of the present invention, the charging station is filled at least partially with a viscous non-conductive and non-magnetic medium of a first density. The charging unit has floating bodies or hollow bodies of a second density which is lower than the first density.
The floating bodies or the hollow bodies ensure that the charging unit essentially floats on the liquid medium. The buoyancy force of the charging unit required for this purpose is the result of a partial immersion of the charging unit in the liquid medium.
Preferably, the at least one, particularly every localization magnet, and the at least one, particularly every positioning magnet, are designed as continuous field magnets. As a result of the arrangement of the at least one localization magnet and of the at least one positioning magnet, the magnetic field orientation of the at least one localization magnet and the magnetic field orientation of the at least one positioning magnet result in an attractive positioning force between the at least one localization magnet and the at least one positioning magnet. By means of the positioning force, a horizontal movement of the charging unit is induced. In a position of the charging unit, which is called a charging position, the potential energy of the positioning magnets in the magnetic field of the localization magnets is locally minimal with respect to the horizontal movement range.
This means, in other words, that the positioning magnets are attracted by the localization magnets. When the charging module is situated in the range of the charging station, the charging unit with the primary coil and the positioning magnets is attracted by the charging module with the secondary coil and the localization magnets. In this case, the charging unit reaches a local minimum of potential energy with respect to its mobility in the x-direction and y-direction in the horizontal movement range, the location of the local minimum being determined by the position of the charging module. Although, if the charging module is not situated in the range of the horizontal movement area, there may be an interaction of the magnetic fields of the localization and positioning magnets, a local minimum of potential energy cannot be taken up by the charging unit in this case. The charging module will therefore then be situated in the range of the horizontal movement area if the charging module takes up position coordinates in the vehicle-fixed coordinate system with respect to the x-axis and y-axis, which position coordinates can be taken up by the mobile charging unit in the same reference system. In other words, in this coordinate system, the charging module will then be situated with respect to the x-axis and y-axis in the horizontal movement range of the charging unit.
If the localization and positioning magnets are electromagnets, according to a special embodiment, the magnets can be energized only if the charging module is moving in this horizontal coordinate range.
According to a further embodiment, the charging station is integrated in the body of the road or the parking space underground. This permits an inconspicuous and space-saving accommodation of the charging station, for example, on public parking lots or in a private garage.
The charging arrangement preferably has a restoring spring between the charging station and the charging unit. The restoring spring exercises a spring force upon the charging unit in the direction of the center of the horizontal movement area. If the charging module is situated in the horizontal movement range of the charging unit, the spring force will be lower than the positioning force.
As a result, it is ensured that the restoring spring positions the charging unit in the horizontal center of the movement area if no vehicle with a charging module is within the range of the charging station. This position is used as the starting position of the charging unit if a charging module of a vehicle to be charged is moved into the range of the charging station.
By means of the described charging arrangement, a charging method can be implemented by which the vehicle first takes up a stopping position in which the charging module is situated in the movement range. In the stopping position, the floating charging unit is attracted by the charging module and the charging position is reached. A battery charging operation will be started when the stopping position (or the charging position) has been reached. This means that the primary coil is fed by an external a.c. network in order to build up a magnetic alternating field. The inductive energy transfer between the primary coil and the secondary coil, in the charging position, is locally maximal with respect to the horizontal movement range.
This charging method offers the vehicle driver the advantage that, for charging the battery, the vehicle is positioned sufficiently precisely above the charging station when the charging module is situated only in the horizontal movement range of the charging unit. The floating charging unit will then automatically be moved into the charging position and is held in the charging position for the charging. In the charging position, the energy transfer between the primary coil and the secondary coil will be maximal. In other words, this means that, if the charging unit is situated in the x-direction and/or y-direction at a distance from the charging position, the energy transfer between the coils will be lower than in the charging position. The charging position therefore forms a local maximum of the transferable electric power.
In a further embodiment of the invention, information can be exchanged between the charging station and the charging module. The exchangeable information contains location data of the vehicle as well as status information of the battery and control variables for a battery charging operation.
The information can be utilized, for example, for assisting the driver when taking up a stopping position by means of navigation instructions. The communication between the vehicle and the charging station can also be used for identifying the vehicle, for example, in order to carry out an automatic billing of the charging operation with the car owner. Such a billing procedure can also be carried out driver-specifically by the identification of a certain vehicle key.
According to a defined further development, the charging station is movable in the vertical direction relative to the vehicle underbody.
Therefore, when the charging position has been reached by the charging unit, the spatial distance can be minimized between the two coils in the vertical direction, i.e. in the direction of the vertical axis of the vehicle, in order to increase the energy transfer from the primary coil to the secondary coil.
The invention is based on the considerations indicated in the following.
Wired charging stations for electric vehicles or plug-in vehicles are inconvenient and can be insufficiently implemented in the public infrastructure. Wireless inductive charging methods so far have had insufficient concepts for an efficient energy transfer and vehicle coupling. The two points require a close linking of the “filling station”, i.e. of the primary carrier side, to the vehicle because of the line loss. In addition, because of the integration into the public infrastructure, such as the road pavement or the underground garage floor, the implementation has to be weather-resistant and compensate a certain “unsharpness” or certain positions of the vehicle to be filled, and thereby minimize charging losses, i.e. “automatically” establish an ideal contact between the charging station and the vehicle.
As an improvement measure, a weather-resistant charging station is to be introduced which contains a charging unit hermetically closed off from the environment. Here, a weather-resistant cast housing made, for example, of PE or PTFE is used, which completely integrates the charging unit. The charging station can be integrated into the public infrastructure (for example, a road pavement) as well as into the private infrastructure (for example, a garage).
In addition, the weather-resistant integrated charging station has a “self-optimizing” positioning of the charging unit relative to the vehicle in order to minimize charging losses and permit arbitrary positions of the charging vehicle.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.